Many mobile telephone devices are capable of playing back voice call content (e.g., in a telephone call) as well as multimedia content (e.g., including music or other audio files, video files, streaming audio, streaming video, video conferencing, etc.). Mobile devices typically include an earpiece and one or more loudspeakers, and are configured to operate in different audio delivery modes based on the operational context. For voice calls, mobile devices may either be operated in a handset mode where audio is delivered at a relatively low volume level over the earpiece (requiring the user of the mobile device to hold the earpiece up to his or her ear), or in a speakerphone mode where audio is delivered at a relatively high volume level over one or more loudspeakers (allowing the user to keep the mobile device away from his or her ears while still hearing the content of the voice call). For multimedia content (e.g., music files), audio is delivered using the one or more loudspeakers. Playback of voice call audio content or multimedia audio content may also be available through a headphone jack, which allows headphones or other external playback devices to be plugged into the mobile device.
Due to the size of mobile devices, the loudspeaker(s) used in such devices are typically limited to playing audio at frequencies within the range of approximately 1 kHz to 20 kHz, and would be very inefficient at or incapable of producing low frequency audio signals having frequencies less than approximately 1 kHz. Accordingly, frequencies lower than 1 kHz are conventionally filtered out by the mobile devices prior to playback at the loudspeaker(s) of the mobile device, so as to avoid excessive distortion to the audio content (and also to avoid potential damage to the loudspeaker(s)). However, filtering out frequencies lower than 1 kHz causes degradation in the quality of a multimedia audio signal, which may, for example, span the frequency range of approximately 20 Hz to 20 kHz.